Zinc mediated reductive dimerization and cyclization of α,β-unsaturated ketones in the presence of a catalytic amount of mercury(II) chloride

The zinc mediated reductive dimerization and cyclization of α,β-unsaturated ketones gives functionalized cyclopentanols in good yield in the presence of a catalytic amount of mercury(II) chloride in N,N-dimethylformamide as solvent at room temperature. The reaction is regio- and stereo-selective producing 3,4-trans-diarylcyclopentanols selectively.     

A convenient single step synthesis of p-thiomethylmethylcalixarenes and metal ion extraction studies

A facile synthesis of p-thiomethylmethylcalixarenes through a [2,5] sigmatropic rearrangement and extraction of soft heavy metal ions using the prepared calix[4]arene derivative is reported here.     

Downstream implicit schemes for advection

Downstream-weighted implicit difference schemes for pure advection are stable for Courant numbers λ ≥ 1. They are numerically diffusive when λ > 1.     

Transverse photon effect in mirror nuclei

We discuss the effect of the interactions of transverse photons with nucleons in a nucleus on the energy difference between mirror pairs of nuclei. The inclusion of this interaction energy reduces the coulomb energy anomaly by about 10% in the mirror pairs of nuclei considered. (A = 13 – 33).     

Substituent effects on thermal decolorization rates of bisbenzospiropyrans

[reaction: see text] A novel application of photochromic molecules is to mimic physiological oscillatory calcium signals by reversibly binding and releasing calcium ions in response to light. Substituent changes on the largely unexplored photochromic bisbenzospiropyran scaffold led to significant changes in thermal fading rates in several organic solvents. Excellent correlations have been found between fading rates and empirical Hammett constants as well as calculated ground-state energies. These correlations can be used to improve scaffold design.     

Intrinsic birefringence of poly(ethylene terephthalate)

In the existing literature various values are given for the intrinsic birefringence of the crystalline and the amorphous phases in poly(ethylene terephthalate) (PET). These values have either been calculated theoretically or obtained from experimental data on the basis of certain models. In this investigation, using the Samuels two-phase model which correlates sonic modulus with structural parameters, intrinsic birefringence values for the crystalline (Δn_c) and amorphous (Δn_a) phases have been determined by studying 30 PET samples prepared by heat setting to have a wide range of structures; the results are Δn_c = 0.29 and Δn_a = 0.20. These values are discussed along with others in the literature and it is concluded that in the light of the present work, the values used by many authors need reexamination.     

Direct α-hydroxylation of ketones using iodosobenzene

Ketones are converted smoothly into the corresponding acyloin with a high degree of selectivity upon treatment with iodosobenzene or phenyliodosodiacetate in methanolic sodium hydroxide.     

Oxidation studies on Andrographolide

Jones oxidation of Andrographolide (1), gave mixture of three products (3-dehydroandrographolide (5), 3,19-bis dehydroandrographolide (6) and 19-dehydroandrographolide (7). Tritylation of andrographolide at C19-OH resulted to products 8 and diene 9, which can be converted to its acetate 10 and oxidation product 11.